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<div class="section" id="module-xml.dom.pulldom">
<span id="xml-dom-pulldom-support-for-building-partial-dom-trees"></span><h1>20.8. <a class="reference internal" href="#module-xml.dom.pulldom" title="xml.dom.pulldom: Support for building partial DOM trees from SAX events."><code class="xref py py-mod docutils literal"><span class="pre">xml.dom.pulldom</span></code></a> — Support for building partial DOM trees<a class="headerlink" href="#module-xml.dom.pulldom" title="Permalink to this headline">¶</a></h1>
<p><strong>Source code:</strong> <a class="reference external" href="https://hg.python.org/cpython/file/3.5/Lib/xml/dom/pulldom.py">Lib/xml/dom/pulldom.py</a></p>
<hr class="docutils" />
<p>The <a class="reference internal" href="#module-xml.dom.pulldom" title="xml.dom.pulldom: Support for building partial DOM trees from SAX events."><code class="xref py py-mod docutils literal"><span class="pre">xml.dom.pulldom</span></code></a> module provides a “pull parser” which can also be
asked to produce DOM-accessible fragments of the document where necessary. The
basic concept involves pulling “events” from a stream of incoming XML and
processing them. In contrast to SAX which also employs an event-driven
processing model together with callbacks, the user of a pull parser is
responsible for explicitly pulling events from the stream, looping over those
events until either processing is finished or an error condition occurs.</p>
<div class="admonition warning">
<p class="first admonition-title">Warning</p>
<p class="last">The <a class="reference internal" href="#module-xml.dom.pulldom" title="xml.dom.pulldom: Support for building partial DOM trees from SAX events."><code class="xref py py-mod docutils literal"><span class="pre">xml.dom.pulldom</span></code></a> module is not secure against
maliciously constructed data. If you need to parse untrusted or
unauthenticated data see <a class="reference internal" href="xml.html#xml-vulnerabilities"><span>XML vulnerabilities</span></a>.</p>
</div>
<p>Example:</p>
<div class="highlight-python3"><div class="highlight"><pre><span></span><span class="kn">from</span> <span class="nn">xml.dom</span> <span class="k">import</span> <span class="n">pulldom</span>
<span class="n">doc</span> <span class="o">=</span> <span class="n">pulldom</span><span class="o">.</span><span class="n">parse</span><span class="p">(</span><span class="s1">'sales_items.xml'</span><span class="p">)</span>
<span class="k">for</span> <span class="n">event</span><span class="p">,</span> <span class="n">node</span> <span class="ow">in</span> <span class="n">doc</span><span class="p">:</span>
<span class="k">if</span> <span class="n">event</span> <span class="o">==</span> <span class="n">pulldom</span><span class="o">.</span><span class="n">START_ELEMENT</span> <span class="ow">and</span> <span class="n">node</span><span class="o">.</span><span class="n">tagName</span> <span class="o">==</span> <span class="s1">'item'</span><span class="p">:</span>
<span class="k">if</span> <span class="nb">int</span><span class="p">(</span><span class="n">node</span><span class="o">.</span><span class="n">getAttribute</span><span class="p">(</span><span class="s1">'price'</span><span class="p">))</span> <span class="o">></span> <span class="mi">50</span><span class="p">:</span>
<span class="n">doc</span><span class="o">.</span><span class="n">expandNode</span><span class="p">(</span><span class="n">node</span><span class="p">)</span>
<span class="nb">print</span><span class="p">(</span><span class="n">node</span><span class="o">.</span><span class="n">toxml</span><span class="p">())</span>
</pre></div>
</div>
<p><code class="docutils literal"><span class="pre">event</span></code> is a constant and can be one of:</p>
<ul class="simple">
<li><code class="xref py py-data docutils literal"><span class="pre">START_ELEMENT</span></code></li>
<li><code class="xref py py-data docutils literal"><span class="pre">END_ELEMENT</span></code></li>
<li><code class="xref py py-data docutils literal"><span class="pre">COMMENT</span></code></li>
<li><code class="xref py py-data docutils literal"><span class="pre">START_DOCUMENT</span></code></li>
<li><code class="xref py py-data docutils literal"><span class="pre">END_DOCUMENT</span></code></li>
<li><code class="xref py py-data docutils literal"><span class="pre">CHARACTERS</span></code></li>
<li><code class="xref py py-data docutils literal"><span class="pre">PROCESSING_INSTRUCTION</span></code></li>
<li><code class="xref py py-data docutils literal"><span class="pre">IGNORABLE_WHITESPACE</span></code></li>
</ul>
<p><code class="docutils literal"><span class="pre">node</span></code> is an object of type <code class="xref py py-class docutils literal"><span class="pre">xml.dom.minidom.Document</span></code>,
<code class="xref py py-class docutils literal"><span class="pre">xml.dom.minidom.Element</span></code> or <code class="xref py py-class docutils literal"><span class="pre">xml.dom.minidom.Text</span></code>.</p>
<p>Since the document is treated as a “flat” stream of events, the document “tree”
is implicitly traversed and the desired elements are found regardless of their
depth in the tree. In other words, one does not need to consider hierarchical
issues such as recursive searching of the document nodes, although if the
context of elements were important, one would either need to maintain some
context-related state (i.e. remembering where one is in the document at any
given point) or to make use of the <a class="reference internal" href="#xml.dom.pulldom.DOMEventStream.expandNode" title="xml.dom.pulldom.DOMEventStream.expandNode"><code class="xref py py-func docutils literal"><span class="pre">DOMEventStream.expandNode()</span></code></a> method
and switch to DOM-related processing.</p>
<dl class="class">
<dt id="xml.dom.pulldom.PullDom">
<em class="property">class </em><code class="descclassname">xml.dom.pulldom.</code><code class="descname">PullDom</code><span class="sig-paren">(</span><em>documentFactory=None</em><span class="sig-paren">)</span><a class="headerlink" href="#xml.dom.pulldom.PullDom" title="Permalink to this definition">¶</a></dt>
<dd><p>Subclass of <a class="reference internal" href="xml.sax.handler.html#xml.sax.handler.ContentHandler" title="xml.sax.handler.ContentHandler"><code class="xref py py-class docutils literal"><span class="pre">xml.sax.handler.ContentHandler</span></code></a>.</p>
</dd></dl>
<dl class="class">
<dt id="xml.dom.pulldom.SAX2DOM">
<em class="property">class </em><code class="descclassname">xml.dom.pulldom.</code><code class="descname">SAX2DOM</code><span class="sig-paren">(</span><em>documentFactory=None</em><span class="sig-paren">)</span><a class="headerlink" href="#xml.dom.pulldom.SAX2DOM" title="Permalink to this definition">¶</a></dt>
<dd><p>Subclass of <a class="reference internal" href="xml.sax.handler.html#xml.sax.handler.ContentHandler" title="xml.sax.handler.ContentHandler"><code class="xref py py-class docutils literal"><span class="pre">xml.sax.handler.ContentHandler</span></code></a>.</p>
</dd></dl>
<dl class="function">
<dt id="xml.dom.pulldom.parse">
<code class="descclassname">xml.dom.pulldom.</code><code class="descname">parse</code><span class="sig-paren">(</span><em>stream_or_string</em>, <em>parser=None</em>, <em>bufsize=None</em><span class="sig-paren">)</span><a class="headerlink" href="#xml.dom.pulldom.parse" title="Permalink to this definition">¶</a></dt>
<dd><p>Return a <a class="reference internal" href="#xml.dom.pulldom.DOMEventStream" title="xml.dom.pulldom.DOMEventStream"><code class="xref py py-class docutils literal"><span class="pre">DOMEventStream</span></code></a> from the given input. <em>stream_or_string</em> may be
either a file name, or a file-like object. <em>parser</em>, if given, must be an
<a class="reference internal" href="xml.sax.reader.html#xml.sax.xmlreader.XMLReader" title="xml.sax.xmlreader.XMLReader"><code class="xref py py-class docutils literal"><span class="pre">XMLReader</span></code></a> object. This function will change the
document handler of the
parser and activate namespace support; other parser configuration (like
setting an entity resolver) must have been done in advance.</p>
</dd></dl>
<p>If you have XML in a string, you can use the <a class="reference internal" href="#xml.dom.pulldom.parseString" title="xml.dom.pulldom.parseString"><code class="xref py py-func docutils literal"><span class="pre">parseString()</span></code></a> function instead:</p>
<dl class="function">
<dt id="xml.dom.pulldom.parseString">
<code class="descclassname">xml.dom.pulldom.</code><code class="descname">parseString</code><span class="sig-paren">(</span><em>string</em>, <em>parser=None</em><span class="sig-paren">)</span><a class="headerlink" href="#xml.dom.pulldom.parseString" title="Permalink to this definition">¶</a></dt>
<dd><p>Return a <a class="reference internal" href="#xml.dom.pulldom.DOMEventStream" title="xml.dom.pulldom.DOMEventStream"><code class="xref py py-class docutils literal"><span class="pre">DOMEventStream</span></code></a> that represents the (Unicode) <em>string</em>.</p>
</dd></dl>
<dl class="data">
<dt id="xml.dom.pulldom.default_bufsize">
<code class="descclassname">xml.dom.pulldom.</code><code class="descname">default_bufsize</code><a class="headerlink" href="#xml.dom.pulldom.default_bufsize" title="Permalink to this definition">¶</a></dt>
<dd><p>Default value for the <em>bufsize</em> parameter to <a class="reference internal" href="#xml.dom.pulldom.parse" title="xml.dom.pulldom.parse"><code class="xref py py-func docutils literal"><span class="pre">parse()</span></code></a>.</p>
<p>The value of this variable can be changed before calling <a class="reference internal" href="#xml.dom.pulldom.parse" title="xml.dom.pulldom.parse"><code class="xref py py-func docutils literal"><span class="pre">parse()</span></code></a> and
the new value will take effect.</p>
</dd></dl>
<div class="section" id="domeventstream-objects">
<span id="id1"></span><h2>20.8.1. DOMEventStream Objects<a class="headerlink" href="#domeventstream-objects" title="Permalink to this headline">¶</a></h2>
<dl class="class">
<dt id="xml.dom.pulldom.DOMEventStream">
<em class="property">class </em><code class="descclassname">xml.dom.pulldom.</code><code class="descname">DOMEventStream</code><span class="sig-paren">(</span><em>stream</em>, <em>parser</em>, <em>bufsize</em><span class="sig-paren">)</span><a class="headerlink" href="#xml.dom.pulldom.DOMEventStream" title="Permalink to this definition">¶</a></dt>
<dd><dl class="method">
<dt id="xml.dom.pulldom.DOMEventStream.getEvent">
<code class="descname">getEvent</code><span class="sig-paren">(</span><span class="sig-paren">)</span><a class="headerlink" href="#xml.dom.pulldom.DOMEventStream.getEvent" title="Permalink to this definition">¶</a></dt>
<dd><p>Return a tuple containing <em>event</em> and the current <em>node</em> as
<code class="xref py py-class docutils literal"><span class="pre">xml.dom.minidom.Document</span></code> if event equals <code class="xref py py-data docutils literal"><span class="pre">START_DOCUMENT</span></code>,
<code class="xref py py-class docutils literal"><span class="pre">xml.dom.minidom.Element</span></code> if event equals <code class="xref py py-data docutils literal"><span class="pre">START_ELEMENT</span></code> or
<code class="xref py py-data docutils literal"><span class="pre">END_ELEMENT</span></code> or <code class="xref py py-class docutils literal"><span class="pre">xml.dom.minidom.Text</span></code> if event equals
<code class="xref py py-data docutils literal"><span class="pre">CHARACTERS</span></code>.
The current node does not contain informations about its children, unless
<a class="reference internal" href="#xml.dom.pulldom.DOMEventStream.expandNode" title="xml.dom.pulldom.DOMEventStream.expandNode"><code class="xref py py-func docutils literal"><span class="pre">expandNode()</span></code></a> is called.</p>
</dd></dl>
<dl class="method">
<dt id="xml.dom.pulldom.DOMEventStream.expandNode">
<code class="descname">expandNode</code><span class="sig-paren">(</span><em>node</em><span class="sig-paren">)</span><a class="headerlink" href="#xml.dom.pulldom.DOMEventStream.expandNode" title="Permalink to this definition">¶</a></dt>
<dd><p>Expands all children of <em>node</em> into <em>node</em>. Example:</p>
<div class="highlight-python3"><div class="highlight"><pre><span></span><span class="kn">from</span> <span class="nn">xml.dom</span> <span class="k">import</span> <span class="n">pulldom</span>
<span class="n">xml</span> <span class="o">=</span> <span class="s1">'<html><title>Foo</title> <p>Some text <div>and more</div></p> </html>'</span>
<span class="n">doc</span> <span class="o">=</span> <span class="n">pulldom</span><span class="o">.</span><span class="n">parseString</span><span class="p">(</span><span class="n">xml</span><span class="p">)</span>
<span class="k">for</span> <span class="n">event</span><span class="p">,</span> <span class="n">node</span> <span class="ow">in</span> <span class="n">doc</span><span class="p">:</span>
<span class="k">if</span> <span class="n">event</span> <span class="o">==</span> <span class="n">pulldom</span><span class="o">.</span><span class="n">START_ELEMENT</span> <span class="ow">and</span> <span class="n">node</span><span class="o">.</span><span class="n">tagName</span> <span class="o">==</span> <span class="s1">'p'</span><span class="p">:</span>
<span class="c1"># Following statement only prints '<p/>'</span>
<span class="nb">print</span><span class="p">(</span><span class="n">node</span><span class="o">.</span><span class="n">toxml</span><span class="p">())</span>
<span class="n">doc</span><span class="o">.</span><span class="n">expandNode</span><span class="p">(</span><span class="n">node</span><span class="p">)</span>
<span class="c1"># Following statement prints node with all its children '<p>Some text <div>and more</div></p>'</span>
<span class="nb">print</span><span class="p">(</span><span class="n">node</span><span class="o">.</span><span class="n">toxml</span><span class="p">())</span>
</pre></div>
</div>
</dd></dl>
<dl class="method">
<dt id="xml.dom.pulldom.DOMEventStream.reset">
<code class="descname">reset</code><span class="sig-paren">(</span><span class="sig-paren">)</span><a class="headerlink" href="#xml.dom.pulldom.DOMEventStream.reset" title="Permalink to this definition">¶</a></dt>
<dd></dd></dl>
</dd></dl>
</div>
</div>
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<h3><a href="../contents.html">Table Of Contents</a></h3>
<ul>
<li><a class="reference internal" href="#">20.8. <code class="docutils literal"><span class="pre">xml.dom.pulldom</span></code> — Support for building partial DOM trees</a><ul>
<li><a class="reference internal" href="#domeventstream-objects">20.8.1. DOMEventStream Objects</a></li>
</ul>
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</ul>
<h4>Previous topic</h4>
<p class="topless"><a href="xml.dom.minidom.html"
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<h4>Next topic</h4>
<p class="topless"><a href="xml.sax.html"
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